1. Field of the Invention
This invention relates to an aerodynamic handlebar extension for bicycles, also known as an “aero bar” or aerobar, and in particular to an aerobar assembly that mounts on the handlebar stem that is part of the fork of the bicycle, rather than on the existing handlebars, and that thereby provides improved adjustability, comfort, and safety.
2. Description of Related Art
The concept of handlebar extensions that permit the rider of a bicycle to assume an improved aerodynamic position, by positioning the riders hands forwardly of the handlebar and by providing support for the riders elbows or forearms, is well-known. Conceived in the mid-1980's, the aerobar was quickly adopted by triathletes. Since Greg LeMond used them in winning the 1989 Tour de France, aerobars have also attained widespread use by bicycle racers, particularly during time trials.
In competitive cycling, proper fitting or adjustment of the aerobar to the rider is critical to achieving optimal performance. In general, the closer the torso of the rider is to horizontal, the lower the aerodynamic drag on the rider. However, the resulting extension of the lower back and hamstrings in the optimal aerodynamic position may cause injury or discomfort to the rider, and may prevent the rider from achieving maximum power. In addition, proper positioning is necessary to ensure clearance for the rider's knees. As a result, the optimal position for racing or triathlons depends on the physiology of the rider, and can vary substantially from rider to rider.
Most currently available aerobars are either nonadjustable or have at best a limited adjustability. While the aerobars of an adjustable aerobar assembly can usually be moved in a fore-to-aft direction to ensure proper horizontal positioning of the rider and accommodate different arm lengths, the elbow rests or pads can only be adjusted laterally, and fail to take into account skew or angling of the rider's arm, either in a horizontal or vertical plane. Furthermore, because the conventional aerobars are either integral with the handlebars or clamped thereto, possibilities for adjustment are limited by the position and configuration of the handlebars.
On the other hand, many conventional aerobar brackets offer too great a lateral tolerance for the aerobars, because the left and right aerobar brackets are mounted independently on the handlebars. This makes it difficult to position the aerobars symmetrically, in a balanced manner, on the left and right sides of the stem.
Another problem with conventional aerobars is the problem of compatibility. Most conventional aerobars are suitable only for a single type of handlebars. Different types of handlebars, e.g., drop bars or bullhorn style TT bars, require different aerobar designs to ensure proper positioning and clamping of the aerobar, provide access to shift levers if stem mounted, and to ensure clearance between the aerobar mount and the knees of the rider.
In addition to the problems of limited adjustability and compatibility, another problem with conventional aerobars is that they can present a significant safety hazard. The cinch clamps conventionally used to secure an aerobar to the handlebars of a bicycle exert a substantial amount of force on the handlebar, in order to counter the rotational torque exerted when the rider leans on the aerobars. This anti-torsion clamping force, combined with vibrations and road shocks, can cause metal fatigue and cracking of the handlebars, while vibrations and shocks also can cause the bolts that secure the clamp to the handlebars to loosen and permit the aerobars so suddenly become loose or fall off.
Furthermore, because the conventional aerobar handlebar brackets must be positioned so that the brackets and aerobars clear the stem, they enable the aerobars to be slid to a position where they extend behind the fork, in the path of the rider's knees. This can also present a serious safety hazard.